1. Field of the Invention
The present invention relates generally to a system and method having a document viewer function, and more particularly, to a system and method for displaying document content using Universal Plug and Play (UPnP).
2. Description of the Related Art
A home network is generally composed of an Internet Protocol (IP)-based private network, which connects and controls various kinds of appliances used at home, such as a Personal Computer (PC), an intelligent device, a wireless appliance, etc., in a network through a common virtual computing environment called middleware.
Middleware connects diverse digital appliances in through peer-to-peer connections and enables the appliances to communicate with one another. Home Audio Video Interoperability (HAVI), UPnP, Java Intelligent Network Infra-structure (JIVI), Home Wide Web (HWW), etc., have been proposed as middleware.
In a computing environment including UPnP middleware, respective appliances are allocated with addresses from a server according to a Dynamic Host Configuration Protocol (DHCP) or addresses selected by an auto Internet Protocol (IP) designation function. The respective appliances communicate with each other and search or inquire on the network through the allocated addresses.
The UPnP network, which is a commonly used home network technology, defines UPnP devices and UPnP services and defines protocols among them. The UPnP network is composed of Controlled Devices (CDs), which are home network appliances that are connected to an IP-based home network to be controlled, and a Control Point (CP), which is an appliance for controlling the controlled devices. More specifically, the control point is a device that controls the controlled devices, and is a constituent element that requests and receives an event. The controlled device performs a predetermined function according to a request of the control point, and is a constituent element that sends the event to the control point that has requested the event when the state of the controlled device is changed.
Operations performed by appliances of a UPnP network include an advertisement process, a discovery process, a description process, a control process, and an eventing process.
The advertisement process is a process in which a new controlled device connects to the home network and informs other devices on the home network of the new controlled device itself. The discovery process is a process in which a new control point connects to the home network and searches for other controlled devices operating on the home network. The description process is a process in which the control point, in order to control the newly added controlled device, obtains, in more detail, functions of the newly added device by parsing a service description eXtensible Markup Language (XML) file or a device description XML file through an IP address of the controlled device obtained in the discovery process. The control process is a process in which the control point, which intends to provide a specified service through the controlled device, transmits a control message (i.e., an “action request”) for requesting a predetermined service using Simple Object Access Protocol (SOAP) in accordance with the UPnP device architecture to the corresponding controlled device, and receives a response message (i.e., “result, variable value”). An eventing process is a process of confirming the information change state of the controlled device that has provided the predetermined service in accordance with the control command transmitted from the control point.
UPnP Audio/Video (AV) transport service technology for enjoying multimedia content, such as audio, video, etc., based on the above-described UPnP technology is described in the UPnP AV specification.
According to the UPnP specification, the UPnP Audio/Video Transport Service (AVTS) architecture defines an operation related to the transmission of audio and video stream, and defines a common A/V transport mechanism that is suitable to a general User Interface (UI) environment. The UPnP AVTS architecture is applicable to a generally used medium, such as a disc, a tape, a compact disc, a Video Cassette Recorder (VCR) cassette, or a Motion Picture Experts' Group Audio Layer—3 (MP3) file.
Specifically, the UPnP AVTS architecture includes a media server providing a multimedia file through a content directory service, a media renderer rendering the provided multimedia file, and the control point controlling the media server and the media renderer, in order for the media server and the media renderer co-operate with each other. The content directory service is a service built into the media server, and provides, to the control point, meta data of content that exists in/out of the home network or is stored in the media server. The control point requests the media renderer to perform rendering by confirming the meta data from the content directory service. For example, as illustrated in FIG. 1, the UPnP AVTS architecture basically performs command operations, such as “PLAY”, “STOP”, and “PAUSE” through commands composed of state variables, such as “NO_MEDIA_PRESENT”, “STOPPED”, “PLAYING”, “TRANSITIONING”, and “PAUSING”.
As described above, according to the UPnP AVTS architecture, the media renderer renders the multimedia file such as audio and video stream provided from the media server, and the control point controls the media renderer and the media server.
However, the conventional UPnP AVTS architecture can only render the multimedia files such as audio and video streams, but does not support a document viewer function for viewing text and documents. Accordingly, there is a need for the document viewer function.
Also, in order to add a document viewer function, the UPnP AVTS architecture may add a state variable for supporting the document viewer by extending the specification of the control point.
However, in the case where a plurality of control points including the UPnP control point and another extended control point both exist within a single appliance, there is a difficulty in that the media renderer must transmit AVTS-related event that occurs in the media renderer itself to all clients.
In addition, transmission of an event that is not related to AVTS may cause a control unit of the control point to malfunction, and according to conventional methods a new function may not be added by merely extending the existing AVTS architecture.